The winding of electrical coils for such devices as transformers, solenoids, inductors, relays and other units have become very highly developed and in many cases have been automated. The production quantities of units utilizing electrical winding of this type run into the millions of units per year on many types and sizes of devices. Obviously, any savings that can be accomplished in the production in this tremendous number of units constitutes a substantial savings on an over-all basis for each year.
Electrical coils wound on winding forms or bobbins has been known and used extensively for many years. In order to make bobbin wound coils from a cost standpoint, it has become necessary to provide an arrangement for leading the initial wire from the center of the bobbin or the winding portion of the form, to an external point or terminal. In the past, expedients such as holes either drilled or formed through the flange of the winding form or bobbin have been utilized. This arrangement has not been satisfactory in that it takes a considerable amount of manual dexterity and time to feed a small wire through such a hole in the beginning of the operation of winding a bobbin. This is especially true in the case of axially spaced bobbins used in supporting separate coils such as the pull coil and push coil used on dual operated solenoids were positive action is sought and controlled by alternatively passing current through the individually wound coils positioned on a supporting sleeve passing through a central opening in each of the spaced-apart wound coil units.
Also in the past, there have been concerns with coaxially spaced bobbins tending to rotate relative to one another, particularly when supported by a tubular sleeve having a circular cross section.
It is an object of the present invention to provide a bobbin type dual winding form that allows all lead lines to lead to and emerge from a single end, particularly when two coils are wound at the same time.
Another feature of the present invention lies in the fact that all parts are interlocked, providing anti-rotation throughout the assembly. The present invention includes magnetic washers positioned between coaxially spaced coils and bobbins, and wherein the washers include apertures and mating protrusions for interlocking arrangement. The interlocking arrangement allows the anti-rotation feature to carry throughout the solenoid assembly. Furthermore, stepped tube ends on inter-fitting bobbin components, and semi-perforated nibs in the magnetic steel spool washers positioned between the coils provide further inter-fitting arrangements.
An improved end cover has been provided for convenience in handling a coiled assembly prior to insertion into a main assembly, and which further protects the lead lines from damage. The end cover is provided with inter-fitting fins, which act in unison with the mating end pieces to further provide improved dielectric insulation.
The present invention further provides a solution to the problem of damage to insulation resulting from cutting and rubbing against burrs and other sharp edges. The solution incorporates a built-in plastic lead wire grommet as part of the bobbin assembly. The grommet provides electrical and mechanical protection of the lead wires, and provides an anti-rotational interlock between the coil assembly and the housing assembly.
The present invention combines several existing solenoid technologies in a unique combination, and further includes several new components.
Presently, solenoid bobbins have been made using rather large individual pieces. The present invention seeks to utilize more numerous, inter-fitting smaller pieces (a number of these being identical in configuration) to decrease the overall cost of manufacture, and thereby incorporate several unique elements to simplify bobbin assembly techniques and also to overcome past shortcoming. The use of inter-fitting segments allows creating a multitude of configurations, by intermixing different segments. This is an attractive means of achieving coil length variations that are common for applications with diverse stroke requirements. Many variations can be generated without the need to retool the most complex and expensive component, the flange with the lead finish labyrinth (discussed infra).
Present manufacture of solenoids requires attaching lead wires to each winding in its own winding space. Usually, lead splicing and holddown is done directly over the magnet wire winding. This procedure requires careful and time-consuming insulation to avoid dielectric breakdown between the splice and the underlying magnet wire. Individual spool assemblies with lead-finish labyrinths on each end may be used in the dual action (two coil) solenoid configuration, as they are now commonly used in single action (one coil) solenoids. The drawback is that, after assembly, the leads are located at each end of the coil. It is necessary to fold one pair of lead lines to an opposite, exit end for assembly into the housing. This is cumbersome and time consuming.
The present invention allows all lead lines to lead to and emerge from a single end. This feature presents a more convenient assembly of components. In the present invention, two coils may be wound at the same time. The start of the first coil is tied to a winding mandrel while the start of a second coil is tied to a molded tab in a bobbin piece. The start of the second coil is also located by a slot in the flange that routes the wire to the lead attachment piece.
As discussed above, another feature of the present invention is that all parts of the present bobbin assembly are interlocked, providing anti-rotation throughout the assembly. In the past, various means including pressed-on washers have been used. The present invention includes washers having protrusions for interlocking arrangement. The interlocking arrangement allows the anti-rotation feature to carry from the housing throughout the entire solenoid assembly. Furthermore, stepped tube ends fit into each other, while semi-perforated nibs in the steel spool washers will allow further inter-fitting arrangements.
The present invention also provides for a unique end cover. The end cover provides convenience in handling the coiled assembly prior to insertion into the main assembly, and further protects the lead lines from damage. The end cover is provided with inter-fitting fins, which act in unison with the mating end piece to further provide improved dielectric insulation.